Missile LGM-118 Peacekeeper

The LGM-118 Peacekeeper, originally designated MX for "Missile, Experimental," emerged from studies in the 1960s aimed at developing a highly survivable Intercontinental Ballistic Missile (ICBM). The core concept was to create a weapon that could withstand a surprise Soviet first strike and retain sufficient capability to retaliate against remaining enemy missile silos. Development focused on achieving high accuracy, rapid re-targeting, and a robust basing mode that would guarantee the system's survivability. While technical aspects of the missile proved successful, the challenge of finding a politically and strategically acceptable basing method persisted throughout its development, leading to numerous proposals ranging from mobile launchers to super-hardened "dense pack" silo configurations. Full-scale development began in the mid-1970s, culminating in a decision in the 1980s to deploy a limited number of missiles in existing, upgraded silos.

As a three-stage, solid-propellant missile, the Peacekeeper represented a significant leap in ICBM technology. It was the first American ICBM to employ a cold-launch system, where the missile is ejected from its silo before first-stage ignition. Its most formidable feature was its Multiple Independently-targetable Reentry Vehicle (MIRV) capability. A single missile was designed to carry up to eleven Mark 21 reentry vehicles, though treaty limitations capped the deployed number at ten. Each vehicle carried a W87 thermonuclear warhead, and an alternative configuration with W78 warheads was also considered but never deployed. The missile’s exceptional accuracy was its defining characteristic, made possible by its highly advanced Advanced Inertial Reference Sphere (AIRS) guidance system. This precision, combined with a post-boost vehicle for maneuvering its warheads, allowed the Peacekeeper to effectively execute counterforce strikes against hardened military targets.

Entering service with the United States Air Force in December 1986, fifty Peacekeeper missiles were deployed in modified Minuteman silos at Francis E. Warren Air Force Base in Wyoming. The initial deployment was marked by delays in the delivery of the sophisticated AIRS guidance system, rendering some of the first missiles non-operational. To address long-term survivability concerns, a "Peacekeeper Rail Garrison" system was developed to place the missiles on mobile train cars, but this program was cancelled with the end of the Cold War. Ultimately, the Peacekeeper's fate was sealed by arms control treaties, specifically START II, which mandated the elimination of MIRV-capable ICBMs. With the single-warhead Minuteman III being a more cost-effective option under these new terms, the Peacekeeper was gradually withdrawn from service. The final missile was deactivated in September 2005, and its advanced warheads were redeployed to the Minuteman III fleet, while its rocket boosters have been repurposed for civilian satellite launch vehicles.